the Philadelphia Centennial Exhibition. 
59 
Fig. 49 is the rim or circle, fastened to the power behind the belt-wheel. 
Fig. 50 shows the hub with arms attached, also weighted balls, friction-block, and 
the stud with small coiled brass spring secured by a thumb-screw at the end to 
regulate the amount of speed. As the speed increases the balls fly out by 
centrifugal force and press the friction-blocks against the rim, which act as a 
brake, as seen at Fig. 49 ; as soon as the machinery is applied and takes the 
power, the balls drop back, and relieve braking. Fig. 51 shows the governor 
complete ; Fig. 50 being fastened on the power-shaft by a set screw inserted 
in the rim of Fig. 49. 
A novel arrangement of running gear for tread-pmvers was shown by Burt, 
Ilildreth and Co., Harvard, Massachusetts ; the patents are held by W. L. Boyes 
and Bros., of Philadelphia, who manufacture the same. The links are made 
with cogs ; and the driving-gear, which is placed some distance from the end, 
and immediately under the propelling power, i.e. the horse's front feet, cogs 
into the chain-links both above and below. By this arrangement the power 
is very directly utilised, the driving-gear is acted upon only by the straight 
or parallel sections of the platform chain, thus entirely avoiding the irregular 
motion of the binding or end sections of the chain. It will be understood 
that the truck-wheels are clear of the track whilst passing from the upper 
to the lower track. The driving-gear also propels the bottom or returning 
sections up the inclined track and around the front end, avoiding the un- 
necessary friction of drawing the lower portion of the chain around the 
front end of the machine, which is so often the cause of unequal tension and 
of a jerking motion. By this arrangement, long sections and large track- 
wheels (7-in. diameter) can be used, and fewer wheels are required, thus 
lessening friction. The advantages claimed, and I think justly, are as fol- 
lows : — 
1st. The truck-wheels are larger in diameter and fewer in number than in 
any other power in this class. 
2nd. The platform chain moves with a smooth and free motion. 
3rd. The returning sections of the chain are driven up their inclined track 
by the main gear, avoiding the loss of power caused by drawing a chain around 
the front end. 
4th. There is no strain on the joints of the chain whilst bending in passing 
the end tracks. 
5th All the pivots, axles and wheels are hardened and smooth, causing 
little friction. 
6th. There are no cross-rods between the treads, to get bent out of place and 
add to the weight of the moving platform. 
7th. The power is applied to the driving-gear on the straight portion of the 
platform, and the weight of the horses acts directly and always in a straight 
line upon the gear to propel the machine with great force. 
Before leaving this part of my subject I must notice an in- 
genious application of a coil-spring to improve the connection 
between the power and the work. This, known as the Eureka 
Coil-Spring, is the invention of Mr. John A. Hafner, of Pittsburg. 
In considering the utility of this apparatus it should be remem- 
bered that the majority of threshing-machines in the States are 
driven by horse-power through horizontal gearing, as many as 
eight or ten horses being employed, but the spring proves 
equally useful when steam is the motive power — allowing of 
the connection by universal joint, which would be otherwise 
impossible. It is not necessary for me to dwell upon the utility 
